Macromolecule pharmaceutical, including proteins, peptide, polysaccharide, nucleic acid, lipids or the combination, are an increasingly important class of drugs to treat various medical conditions. The primary route for administrating macromolecular pharmaceuticals is injection, which is unpleasant, expensive and often results in poor patient compliance. Oral delivery is a preferred route to administer medicine. However, macromolecular drugs are poorly absorbed through intestines and can be easily destroyed by stomach acid or gastrointestinal enzymes. A promising approach to overcome the barriers for oral macromolecule delivery is to use nano-particles, which may offer protection from degradation and enable absorption of macromolecule drugs.
It has been reported that nano-particles loaded with insulin can be used to deliver bioactive insulin to animals. For example, prevention of plasma glucose elevation by insulin loaded into poly(lactide-co-glycolide) nano-particles with fumaric anhydride oligomer and iron oxide additives has been shown. Carino et al, Controlled Release 65:261, (2000). Another example of oral delivery of insulin with Chitosan nano-particles is provided by Pan et al., Intl. J. Pharmaceutics, 249:139, (2002). In addition, polyalkylcyanoacrylate nanocapsules have also been reported to be an effective carrier for oral delivery of insulin in diabetic animals. Damge et al. Diabetes, 37:246, (1988). The uptake of particulate materials by gastrointestinal route is documented and lymphatic Peyer's patches are involved. Hussain et al., Adv. Drug Delivery Rev. 50:107, (2001).
Among the factors affecting absorption of particles, particle size appears to be the primary factor. For example, Jani et al. (J. Pharm. Pharmacol. 42:821, 1990) studied the intestinal absorption of polystyrene particles of various sizes in rats. The absorption efficiency of polystyrene particles is clearly depending on the size. Particles less than 100 nm showed significant absorption, while large particles (500 nm or more) only showed moderate to low absorption.
The size dependence on particle intestinal absorption is also observed in poly(lactide-co-glycolide) or PLGA particles by Desai et al. (Pharm. Res. 13:1838, 1996). In this study, PLGA particles larger than 500 nm showed virtually no uptake via intestinal tract, yet 36% of PLGA particle of 100 nm was absorbed.
Nanometer scale particles have been proposed for use as carrier particles for biological macromolecules such as proteins and nucleic acids. See U.S. Pat. Nos. 5,178,882; 5,219,577; 5,306,508; 5,334,394; 5,460,830; 5,460,831; 5,462,750; 5,464,634, 6,355,271.
Calcium phosphate particles are bio-adhesive/biocompatible and have been routinely used as carrier to deliver nucleic acid into intracellular compartments in vitro. Chen et al., Mol. Cell. Biol. 7:2745-52, (1987); Welzel et al., J. Mater. Chem. 14:2213-2217 (2004); Jordan et al., Nucleic Acids Research 24:596-601 (1996); Loyter et al., Exp. Cell Res. 139:223-234 (1982). In addition, calcium phosphate has also been tested as carrier for genetic therapy to delivery large nucleic acid in vivo. Roy et al., Intl. J. Pharmaceutics 250:25, (2003).
Therapeutic calcium phosphate particles have been described. U.S. Pat. Nos. 6,355,271; 6,183,803; U.S. Pub. Nos. 2004/0258763; 2002/0054914; 2002/0068090; 2003/0185892; 2001/0048925; WO 02/064112; WO 03/051394; WO 00/46147; WO 2004/050065; Cherian et al., Drug Development and Industrial Pharmacy 26:459-463 (2000). The effect of oral formulation of insulin loaded calcium phosphate particles is tested in diabetic mice and control of blood glucose has been shown. Morcol et al., Intl. J. Pharmaceutics 277:91, (2004). The calcium phosphate particles disclosed have particle size between 300 nm to 10 um. The animal study used particle size in the range of 2-4 um in average. These particle sizes are clearly not optimal.
To make calcium phosphate particles with desired size, extensive sonication is required (Cherian et al. Drug Dev. Ind. Pharmacy, 26:459, 2000; Roy et al. Intl. J. Pharmaceutics 250:25, 2003), which may damage macromolecule drugs encapsulated and is not compatible to co-precipitation procedure.
Furthermore, the encapsulating efficiency of macromolecules into calcium phosphate particles is often low. For example, U.S. Pat. No. 6,355,271 discloses absorption efficiency of about 40% if insulin is added to preformed calcium phosphate particles; and about 89%, if insulin is mixed during the particle formation.
These reported methods either result in particles with less optimal size, or require harsh conditions such as extended sonication that are not compatible to macromolecule formulation. Therefore, there remains a need for oral macromolecule delivery system that is highly efficient and easily produced with low cost.